What is the number of observations per sample(the "n' you use in formulas or tables) you would use here?

Emory, GA Tech, MIT, and CMU compete in a music machine learning (ML) competition annually to find out which team can best use ML to classify music into genres. A panel of experts first identify the genre across 100 randomly selected music pieces (one music piece to one genre). The teams then write algorithms to match the genre identified by the experts. Team scores (number of music pieces correctly matched) across the years are shown below